State and federal transportation officials are touring the Connecticut site where two Metro-North trains packed with rush-hour commuters collided in an accident Friday that sent about 70 people to the hospital, severely damaged the tracks and threatened to snarl travel in the congested Northeast Corridor. Three patients remained in critical condition Saturday morning, with two of those stable, according to officials at two Bridgeport hospitals. About 700 people were on board the Metro-North trains when one heading east from Grand Central Station to New Haven derailed about 6:10 p.m. just outside Bridgeport, MTA and Bridgeport officials said. The train was hit by a train heading west from New Haven to Grand Central on an adjacent track, MTA spokesman Aaron Donovan said. Some cars on the second train also derailed as a result of the collision.